Electromigration and complete gap-fill in IC conductor paths are increasingly important issues as the size of the interconnect conductor paths, which may conventionally range from hundreds to tens of microns wide and even smaller, are minimized in size for IC production and design. Electromigration occurs when some of the momentum of a moving electron is transferred to a nearby activated ion. This causes the ion to move from its original position. Over time this force knocks a significant number of atoms far from their original positions. A break or gap can develop in the conducting material, preventing the flow of electricity. In narrow interconnect conductors, such as those linking transistors and other components in IC, this is known as a void or internal failure open circuit. Electromigration can also cause the atoms of a conductor to pile up and drift toward other nearby conductors, creating an unintended electrical connection known as a hillock failure or whisker failure (short circuit). Both of these situations can lead to a malfunction of the circuit. Additionally, the methods conventionally used in creating the interconnect conductors may result in incomplete fill of channels or gaps for the conductors, which can result in decreased reliability and susceptibility to electromigration. Material choice and manufacturing methods also affect electromigration, where the choice of materials and techniques for placing the materials tend to affect resistance to electromigration effects.
Together with the following description, the Figures demonstrate and explain the principles of the apparatus and methods described herein. In the Figures, the thickness and configuration of components may be exaggerated for clarity. The same reference numerals in different Figures represent the same component.